1. Field of The Invention
The invention relates to an automatic gain control circuit for amplifying an input signal so that it has a specific correspondence with a reference value, the circuit comprising input means for receiving the input signal; variable gain amplifier means for amplifying said input signal in response to a gain control signal; peak detector means for detecting peaks in said amplified input signal, the peak detector means having an attack time constant and a decay time constant, so as to supply a peak detector output signal which is representative of the amplitude of the peaks in said amplified input signal; comparator means for comparing the peak detector output signal with said reference value so as to derive an error signal therefrom; and integrator means for integrating the error signal so as to form said gain control signal.
The invention also relates to a hard disk drive apparatus provided with the automatic gain control circuit.
2. Description of The Related Art
An automatic gain control circuit as defined in the opening paragraph is well known in the art and can, as an example, be used in a servo demodulator circuit in a hard disk drive.